Photoluminescence of Tb3+ and Mn2+ activated Ca8MgGd(PO4)7 under vacuum ultraviolet excitation

Novel Tb3+ and Mn2+ activated Ca8MgGd(PO4)7 phosphors were synthesized by solid-state reaction and their photoluminescence properties in vacuum ultraviolet region were investigated for the first time. It can be observed from the excitation spectra that the host-related absorption band is located around 170 nm, and it overlaps the O2− → Tb3+ charge transfer band of Ca8MgGd(PO4)7:Tb3+ around 161 nm and the 3d5 → 3d44s transition band of Ca8MgGd(PO4)7:Mn2+ near 200 nm. The 4f–4f 5d spin-allowed and spin-forbidden transitions of Tb3+ are verified to be located at 170–250 and 257–271 nm, respectively. Upon 147 nm excitation, the dominant emission peak intensity of the Ca8MgGd0.1(PO4)7:0.9Tb3+ phosphor is about 2.7 times stronger than that of the commercial Zn2SiO4:Mn2+ green phosphor, and the brightness of the former with a short decay time of 2.5 ms is about 98% of the latter’s. The Ca8MgGd(PO4):Mn2+ phosphor excited at 147 nm exhibits a deep red emission around 650 nm, which could be attributed to the 4T1 → 6A1 transition of Mn2+, with the CIE index (0.679, 0.321). In a word, the results above indicate that both Tb3+ and Mn2+ activated Ca8MgGd(PO4)7 phosphors could be promising for PDP or Hg-free lamp applications.

► The Ca8MgGd(PO4)7:Tb3+ shows a comparable brightness with commercial Zn2SiO4:Mn2+.
► The Ca8MgGd(PO4)7:Tb3+ shows a shorter decay time than commercial Zn2SiO4:Mn2+.
► The Ca8MgGd(PO4)7:Tb3+, Mn2+ can be promising for PDP or Hg-free lamp application.